The outer space has proven to be a harsh environment for electronic circuits. When satellites, space shuttles, space probes, etc. leave the Earth's atmosphere, the electronic equipment they carry becomes subject to levels of ionizing radiation that are much higher than those found near the Earth's surface. These high radiation levels are known to alter logic states of components within integrated circuits, which may in turn lead to performance degradation and even catastrophic failure. Ionizing radiation also presents problems in other environments, such as, for example, nuclear facilities (e.g., due to the presence of radioactive materials), X-ray rooms, particle accelerators, and the like.
Generally speaking, ionizing radiation includes particles and/or electromagnetic waves that contain enough energy to cause electrons to detach from atoms or molecules, thus “ionizing” them. Examples of ionizing particules include alpha particles, beta particles, neutrons, cosmic rays, etc. These types of particles typically have much higher energy than other, lower-level types of radiation, such as visible light, infrared light, radio waves, etc.
In some cases, shielded packaging may be used to protect an integrated circuit from radiation exposure. The effectiveness of a shielded package may vary widely depending upon its particular design, materials, etc. As a rule of thumb, however, better shielding is achieved with heavier, bulkier packaging. In other cases, the physical size of devices (e.g., transistors, etc.) fabricated within the integrated circuit may be increased in an attempt to reduce their sensititivity to radiation. Typically, the larger the size of a device, the better its immunity or tolerance to radiation. Large device sizes, however, also increase capacitance and therefore decrease the speed at which an integrated circuit can operate.